Stress and anxiety reactivity as a function of ovarian hormones in the female rat

Abstract

Female rodents and primates have an ovulatory cycle, such that they are able to reproduce when in a particular hormonal state. Many behavioral differences are observed in many species as a function of hormonal state, including, for example, sexual receptivity, aggression, and anxiety. Interestingly, sexual behavior and stress reactivity appear to be mutually inhibitory processes, whereby sexually non-receptive rats will attend more to stress stimuli, and sexually receptive rats will attend primarily to the sexual stimuli. In the current set of experiments, the differences in expectancy of anxiety and stress reactivity as a function of ovarian hormone was explored in the female rat. The results indicate that contextual conditioned fear is more robust in non-sexually receptive females, lending more support to the notion of mutually inhibitory processes. The current findings also indicate that benzodiazepines were effective in reducing stress reactivity in hormone-treated rats, suggesting that GABA may interact with estrogen and/or progesterone to reduce conditioned fear and stress reactivity. Perhaps in primates there is a similar underlying mechanism, where a dysfunction in the interaction between ovarian hormones and GABA modulates the increased anxiety and stress seen in some women and primates premenstrually.